Sound volume regulator



Feb. 5, 1935. J. BETHENOD 1,990,060

' SOUND VOLUME REGULATOR Filed April 9. 1931 [2 mmr QASE/J/ Beffiezzad Emm Patented Feb. 5, 1935 UNITED STATES PATENT OFFICE SOUND VOLUMZE REGULATOR Application April 9, 1931, Serial No. 528,779

In France April 12, 1930 3 Claims.

The present invention relates to improvements in apparatus for regulating the volume of sound produced in gramophones and similar apparatus employing electric amplifiers (generally ther- 5 mionic valve apparatus). The invention provides a regulation under much more satisfactory conditions than those obtaining with hitherto known methods and will be readily understood with reference to the accompanying diagram which illustrates an installation arranged according to this invention.

Referring to the diagram, a gramophone pick-up 1 of the well-known electromagnetic type is arranged to deliver current to a group of inductance windings 2, coupled in series with one another. In order to regulate the volume of sound emitted by a loudspeaker connected to the pick-up through the medium of an electronic amplifier, a commutator 3 is provided, the contacts of which are electrically connected to the bobbins 2 as indicated.

The variable potential which may thus be delivered to the leads 4, 5, bears a constant relationship to the electromotive force induced in the pick-up whatever may be the selected position of the movable rider of the commutator 3, provided that the time constant of each of the bobbins 2, that is, the relation of the inductance thereof to the ohmic resistance is of relatively the same value as that of the winding of the pick-up itself, which it is always possible to ensure. If, for example, the potential thus obtained is applied to the grid circuit of a three electrode valve 6 which is arranged to supply the amplifier feeding the loudspeaker; a perfect solution of the problem of the control of the volume of the sound is thus obtained in a very simple manner, since it is suflicient to actuate the handle of the rider of the commutator 3 to produce an efiect comparable to that which would be obtained theoretically if it were possible to modify directly at will the electromotive force produced in the pick-up without altering 5 the constants of the various circuits involved. Naturally, the number and the constitution of the windings 2 are arbitrary according to circumstances; on the other hand, it is possible in constructing the windings 2, to depart intentionally from the time constant of the pick-up itself with a view to the production of certain desired results in the sound produced by the loudspeaker.

What is claimed is:

1. Means adapted to regulate the volume of sound produced by a phonographic apparatus provided with an electrical pick-up, comprising the combination of a plurality of separate and distinct self-inductive coils which individually have a time constant substantially equal to that of the pick-upand which coils as a group are connected in series in the output circuit of the pick-up, means for applying at least a portion of the total self-inductance of all of said coils by 1 applying the entire self-inductance of at least one of said coils to the input circuit of a thermionic tube amplifier including a switch member in said input circuit and individual leads connected to said coils, with each of which leads said switch member may be brought into contact, at will, and means provided by said amplifier for indicating the volume of sound.

2. Means adapted to regulate the volume of sound produced by a phonographic apparatus provided with an electrical pick-up, comprising the combination of a plurality of separate,'distinct, resistant and self-inductive but nonmutually inductive coils which individually have a time constant substantially equal to that of the pick-up and which coils as a group are connected in series in the output circuit of the pickup, means for applying at least a portion of the total self-inductance of all of said coils by applying the entire self-inductance of one or more of said coils to the input circuit of a thermionic tube amplifier, and means provided by said amplifier for indicating the volume of sound.

3. Means adapted to regulate the volume of sound produced by a phonographic apparatus provided with an electrical pick-up, comprising the combination of a plurality of separate, distinct, resistant and self-inductive but non-mutually inductive coils which individually have a time constant substantially equal to that of the pick-up and which coils as a group are connected in series in the output circuit of the pick-up, means for applying at least a portion of the total self-inductance of all of said coils by applying the entire self-inductance of one or more of said coils to the input circuit of a thermionic tube amplifier including a switch member in said input circuit and individual leads connected to said coils with each of which leads said switch member may be brought into contact, at will, and means provided by said amplifier for indicating the volume of sound.

JOSEPH BETHENOD; 

